Diet is a risk factor for many cancers. However, the appropriate latent period for dietary risk factors is unknown. A strength of the NHS database is the availability of repeat dietary information over 30+ years. One goal of this application (aim 1) is to obtain optimal methods of weighting repeated measures of diet over a 30 year period using an exponential smoothing weighting function. This approach will also be applied to non-dietary exposures such as cigarette smoking and hormone use over a long period of time. Another innovation in cancer epidemiology is the availability of multiple tumor markers which can refine the epidemiology of specific cancers according to tumor type, and help confirm the causality of an association. However, as the number of tumor markers gets large, the number of subsets of tumors also gets large. In aim 2, we propose survival analysis methods to estimate the 2-way interaction between risk factors and tumor types as well as 3-way interactions between risk factors and combinations of tumor types. Improvements in cancer risk prediction are increasingly occurring with novel risk factors measured in case-control datasets. Aim 3 of this application combines information on novel risk factors in case/control datasets with standard risk factors in prospective datasets to improve risk prediction. For breast cancer, an Important predictor is age at menopause. However, this is only known for women with natural menopause and bilateral oophorectomy. In aim 4, we seek to estimate age at natural menopause among other surgical menopause women to reduce bias and enhance precision of breast cancer risk prediction. In aim 5, we will extend the colon cancer risk prediction model developed in the previous cycle of this grant, by developing separate models for proximal cancer, distal cancer and rectal cancer. We also consider novel methods of analysis of recurrent colorectal adenoma outcome data using interval censored survival methods. This Project will interact closely with Projects 1-3 to improve our understanding of the etiology of breast, colorectal and ovarian cancers in women. It also shares with the other Projects a strong administrative and scientific infrastructure provided by Cores A (cohort follow-up and data base maintenance), B (confirmation of cancer and cause of death), C (management of the biospecimens) and D (leadership and data analysis).